It isn't, and I get the feeling you may not have really read my post here and on PR I linked to -
the whole issue is whether or not Walitt believes this is pathogenic, and I'm afraid the paper doesn't say that.
We speculate that a variety of well-defined neuronal mechanisms enable peripheral cytokines to induce central cytokine changes, which trigger a subsequent cascade of neurological events as described below that lead to the
experience of chemobrain
the authors hypothesize that the administration of chemotherapy agents initiates a cascade of biological changes, with short-lived alterations in the cytokine milieu inducing persistent epigenetic alterations (
Fig. 2). These epigenetic changes eventually lead to gene expression changes, altering metabolic activity and neuronal transmission
that are responsible for generating the subjective experience of cognition.
Note 'experience of' and no mention of pathogenic. Also, the contrast with neurologic injury in the paper, as I pointed out in my other posts.
Couple of quotes from the paper to help you out - think they make the authors' views very clear: normal not pathological
The essential questions underlying the validity of the hypotheses underlying the current chemobrain concept, that of direct causality and neuronal injury, are not answered by the scientific literature to date.
The discordance between the severity of subjective experience and that of objective impairment is the hallmark of somatoform illnesses, such as fibromyalgia and chronic fatigue syndrome. A somatoform view of chemobrain would consider it as an atypical yet predictable subjective experience that result from the normal functioning of the brain rather than from an injury. In this way, physiologic factors other than direct neurotoxicity from chemotherapeutic agents are the critical ones in establishing and maintaining chemobrain. Chemotherapy, or the psychological ramifications of cancer treatment, may simply be one of a variety of “triggers” that ultimately lead to dyscognition.
The implications of this observation are that specific chemotherapeutic-related neurologic injury is not required to create the somatic experience of chemobrain.
Any chance you could respond to this key point of pathogenic vs physiologic (normal)?
Few other specific replies, afraid I don't have the energy to make pretty
He doesn't say immune activation in the brain (what others argue), merely cyotkines trigger a cascade leading to neuro changes, pointedly ignoring microglia and immune activation.
And he clearly doesn't invoke the microglia as you claimed - which others are saying is a pathogenic mechanism (evidence from this in rat models following immune stimulation), but he just makes hand-waving claims about epigenetics. And fails to explain why it's not pathogenic.
Epigenetics is real and important. The vogue bit is ascribing anything you can't explain to epigenetics, a catch-all solution to ignorance. It might explain your problem, but evidence is needed.
That's not in question. Epigenetics is involved in many, many processes. The authors could just as easiiy say "it's all down to gene expression". Well, yes. I dare say many specifc protein receptors and transmitters play key roles too. But what's the evidence the cytokine spike causes non-pathogenic, physiologic changes? Like I say, the microglia hypothesis at least has animal model evidence to support a pathogenic role. They are junking one hypothesis with limited evidence for a new one with no specifc evidence linking it to chemobrain or mecfs.
Note how even this quote (not directly linked to chemobrain) is highlighting epigenetics role in a pathological process, not the normal one Walitt and co argue for.